The present invention is generally related to control of internal combustion engines, and, more particularly to, control techniques and system for determining angular crankshaft position prior to a cranking event in the engine.
In internal combustion engines, such as those commonly used in automotive applications, that are controlled by an Engine Control Module (ECM), among other parameters, the ECM generally controls spark firing, and fuel flow to the cylinders of the engine. In order to provide spark firing at exactly the proper time and to the appropriate cylinders, crankshaft position sensors, such as inductive sensors, are provided to indicate to the ECM the angular position of the crankshaft of the engine. Unfortunately, the inductive sensors typically used in automotive applications may have a dead-band at low engine speeds and may only supply a useful signal until the engine speed is greater than a certain non-zero engine speed, typically at least 50 rpm or more. Thus, in a normal engine start, the starter motor begins a cranking event, and eventually accelerates the engine above 50 rpm, at which time the ECM is then able to determine which cylinders are on a compression stroke and should receive spark firing. The above-identified sensing scheme generally results in engine-start cranking times of typically one second or more.
In a land-based vehicle, such as an electric or hybrid electric vehicle that may be equipped with an Integrated Starter Generator (ISG) subsystem (also referred to as Start/Stop Generator (SSG) subsystem, as part of its propulsion drive system, it would be desirable to provide engine-start cranking times not subject to the starting limitations of existing crankshaft sensors. For readers who desire background information regarding innovative propulsion systems equipped with an ISG subsystem and having a relatively wide speed range, high torque per ampere, high efficiency, quick dynamic response, and operational robustness and reliability under tough environmental or operational conditions, or both, reference is made to U.S. patent application Ser. No. 09/928,613 filed Aug. 13, 2001; and Ser. No. 09/909,356 filed Jul. 19, 2001, commonly assigned to the assignee of the present invention, and herein incorporated by reference.
Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof a method for determining angular crankshaft position prior to a cranking event of an internal combustion engine. Upon issuance of an engine shutdown command, the method allows determining an initial crankshaft position based on a crankshaft position sensor. The method further allows providing a rulebase for relating angular travel of a rotor in an accessory device to crankshaft angular travel. Angular travel of the rotor in the accessory device is sensed upon issuance of the engine shutdown command until the engine reaches a resting position. The rulebase is accessed to relate the value of the angular travel of the rotor in the accessory device to crankshaft angular travel and provide an incremental crankshaft angular travel relative to the initial crankshaft position at engine shutdown. Crankshaft position is calculated at the resting position based upon the initial crankshaft position plus the incremental crankshaft angular travel based on the angular travel of the rotor in the accessory device. The calculated crankshaft position corresponding to the resting position is stored. Upon issuance of an engine re-start command, the stored crankshaft position corresponding to the resting position is retrieved to provide quick and accurate engine control regardless of any dead-band in the crankshaft position sensor during low engine speeds.
The present invention further fulfills the foregoing needs by providing in another aspect thereof, a control system for determining angular crankshaft position prior to a cranking event of an internal combustion engine. The controller includes a crankshaft position sensor configured to provide an initial crankshaft position upon issuance of an engine shutdown command. A rulebase is provided for relating angular travel of a rotor in an accessory device to crankshaft angular travel. A rotor position sensor, such as a Hall-effect or magneto-resistive sensor, is provided for sensing angular travel of the rotor in the accessory device upon issuance of the engine shutdown command until the engine reaches a resting position. A processor is configured to access the rulebase to relate the value of the angular travel of the rotor in the accessory device to crankshaft angular travel and provide an incremental crankshaft angular travel relative to the initial crankshaft position at engine shutdown. The processor is further configured to calculate crankshaft position at the resting position based upon the initial crankshaft position plus the incremental crankshaft angular travel based on the angular travel of the rotor in the accessory device. Memory allows storing the calculated crankshaft position corresponding to the resting position. An engine control module is configured to retrieve the stored crankshaft position corresponding to the resting position upon issuance of an engine re-start command, and provide quick and accurate engine control regardless of any dead-band in the crankshaft position sensor during low engine speeds.
In yet another aspect thereof, the present invention provides a computer-readable medium including instructions for causing a computer to determine angular crankshaft position prior to a cranking event of an internal combustion engine by: upon issuance of an engine shutdown command, determining an initial crankshaft position based on a crankshaft position sensor; sensing angular travel of a rotor in an accessory device upon issuance of the engine shutdown command until the engine reaches a resting position; accessing a rulebase configured to relate the value of the angular travel of the rotor in the accessory device to crankshaft angular travel and provide an incremental crankshaft angular travel relative to the initial crankshaft position at engine shutdown; calculating crankshaft position at the resting position based upon the initial crankshaft position plus the incremental crankshaft angular travel based on the angular travel of the rotor in the accessory device; storing the calculated crankshaft position corresponding to the resting position; and, upon issuance of an engine re-start command, retrieving the stored crankshaft position corresponding to the resting position and provide quick and accurate engine control regardless of any dead-band in the crankshaft position sensor during low engine speeds.